Wall correction for a supercritical airfoil in the low speed wind tunnel

One of the most important reasons for the difference between the results of wind tunnel experiments and flight conditions is the effect of the wind tunnel walls. The walls in the test section affect the air flow in the longitudinal and lateral directions, causing a difference between the measured values ​​and the free stream. In this paper, the effects of blockage associated with an supercritical airfoil in a steady state for different attack angles have been investigated and a specific method for correcting the effects of walls has been developed. The Experiments were carried out in a low speed and closed circuit wind tunnel at a speed of 30 m / s and Reynolds No. equal to 600,000 using the pressure distribution measurement on the model and the tunnel wall. Using the pressure distribution on the tunnel wall, the flow field around the model with source and sink potential was estimated approximately. Then, using a rapid algorithm, the distribution of these potentials was calculated along the central line of the tunnel and finally corrected by calculating the effects of blockage, pressure distribution on the model, dynamic pressure and measured aerodynamic coefficients. Also, modified aerodynamic coefficients were compared with each other separately. The results obtained from these two methods differed slightly in relation to the attack angles, with the highest difference of 7% in the angle of attack of 20 degrees. Also, the developed methods indicated the accuracy of the corrections on the aerodynamic coefficients.